JP2016125384A - Exhaust system of engine drive type work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a repetition degree in forcible regeneration, improve fuel consumption and reduce exhaust sound at an engine drive type work machine including a continuous regeneration type exhaust gas after-treatment device.SOLUTION: An exhaust system 30 is formed by an exhaust gas after-treatment device 31 having an inlet 31a communicated with an exhaust port 23 of an engine 20 within an engine chamber 10a; an exhaust pipe 32 communicated with an outlet 31b of the device 31 and extended up to an exhaust gas chamber 10b; a muffler 33 communicated with the exhaust pipe within the exhaust gas chamber; and a tail pipe 34 communicated with an outlet of the muffler. An exhaust resistance of an entire exhaust system is increased by the muffler, and an inlet temperature of the device 31 is increased due to arrangement of the device 31, a continuous regenerating efficiency during a normal operation is improved, a repetition degree of forcible regeneration is decreased and the device 31 and the muffler are spaced apart to cause the exhaust gas to be preferably cooled during transferring operation, a flow rate of the exhaust gas at a tail pipe outlet is decreased and exhaust sound is also substantially decreased during the forcible regeneration.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an exhaust system for an engine-driven work machine, and more particularly, an exhaust gas aftertreatment device for removing particulate matter (hereinafter referred to as “PM”) in the exhaust gas is included in the system configuration. , It relates to the exhaust system of engine-driven work machines.

  In an engine-driven work machine equipped with a work machine such as a compressor or a generator and an engine that drives the work machine, a diesel engine is generally adopted as an engine that drives the work machine. In addition, a lot of PM is discharged with the exhaust gas at the time of combustion compared to the gasoline engine.

  Since this PM causes air pollution and health damage, a regulation value (mass per unit output [g / kWh]) of PM discharged from a diesel engine is determined by exhaust gas regulations.

  In order to comply with the above emission regulations, an exhaust gas aftertreatment device having a filter called a diesel particulate filter (hereinafter referred to as “DPF”) is provided in the exhaust passage of a diesel engine. Emissions are being reduced.

  Since this exhaust gas after-treatment device reduces the amount of PM emission by collecting PM in the exhaust gas using the built-in DPF, the PM deposition on the DPF advances as the use continues. Cause clogging.

  If the exhaust resistance increases due to this clogging, the engine output decreases and the fuel consumption deteriorates. Therefore, it is necessary to remove the accumulated PM and regenerate the DPF.

  As one of such DPF regeneration methods, an oxidization catalyst (Diesel Oxidation Catalyst: hereinafter referred to as “DOC”) is provided on the inlet side in the exhaust gas after-treatment device, and the DPF is accommodated on the downstream side thereof. An exhaust gas aftertreatment device called “continuous regeneration type” that continuously regenerates DPF by the catalytic action of the above has been proposed.

This continuous regeneration type exhaust gas aftertreatment device generates NO ₂ by the action of the DOC when the temperature of the DOC rises above the activation temperature due to the heat of the exhaust gas of the engine during normal operation of the engine-driven work machine. By burning PM using NO ₂ as an oxidizer, DPF can be regenerated at a temperature lower than the self-combustion temperature of oxygen by oxygen, and PM is continuously burned by the heat of exhaust gas during engine operation. (Hereinafter, the regeneration of the DPF that is continuously performed during the normal operation of the engine-driven work machine is referred to as “continuous regeneration”).

  However, even in such a continuous regeneration type exhaust gas aftertreatment device, the exhaust gas temperature introduced into the DOC is increased by the DOC activation temperature, for example, when the engine is operated for a long time in a low-load operation state. When the operation is continued for a long time in a state where the temperature is lower than the range, the function of continuous regeneration is not exhibited and PM cannot be combusted, so that PM deposition proceeds on the DPF.

  Then, after PM exceeding a certain amount accumulates on the DPF and the exhaust resistance increases, when the engine shifts to high load operation, the exhaust gas temperature becomes lower than that during normal high load operation due to the high exhaust resistance. A large amount of PM deposited on the DPF starts self-combustion and generates a high temperature, and this heat causes cracks and erosion of the DPF.

Therefore, even in the continuously regenerative exhaust gas aftertreatment device, when the amount of PM deposited on the DPF exceeds a predetermined amount, the exhaust gas temperature is increased by delaying the fuel post-injection or injection timing, and the exhaust gas after-treatment device. A forced regeneration method is also used in which the PM deposited on the DPF is forcibly burned using NO ₂ as an oxidant by raising the temperature of the DOC above the activation temperature (Patent Document 1). ).

Note that the forced regeneration method described in Patent Document 1 described above is a forced regeneration that is performed in a state where the load on the engine fluctuates, such as during driving of an automobile (hereinafter referred to as “load fluctuation type forced regeneration”). In such a load-variable forced regeneration, if forced regeneration is started with the engine running at a low load and the exhaust gas temperature is low, it takes a long time to complete the regeneration of the DPF. fuel injection amount is increased or decreased by post injection, or can not maintain state temperature is equal to or higher than the activation temperature becomes unstable oxidation catalyst by repeating the operation in which post-injection is stopped at a temporary high load operation, NO ₂ May not be able to be generated stably / continuously, and PM may not be completely combusted. Furthermore, if the operator stops the engine even though forced regeneration is being performed, Since the regeneration of the DPF is also interrupted, the PM deposited on the DPF may not be completely removed and the PM may still be accumulated. In view of the possibility of damage, the applicant of the present application uses a warning light that indicates that a predetermined amount or more of PM has accumulated on the DPF as a regeneration method for the exhaust gas aftertreatment device provided in the engine driven compressor. Based on lighting, etc., the operator performs a switch operation for instructing the start of forced regeneration, etc., so that the load on the engine is kept constant, and thus the forced regeneration performed with the temperature inside the DPF stabilized ( Hereinafter, such a forced regeneration is referred to as “constant load type forced regeneration”), and an application for a regeneration method for an exhaust gas aftertreatment device has been filed (Patent Document 2).

  As described above, the regeneration of the DPF requires the DOC temperature to be equal to or higher than the activation temperature. Therefore, the DOC temperature is easily maintained within the activation temperature as described above. An engine-driven work machine in which the arrangement of the exhaust gas aftertreatment device is devised has also been proposed.

  As such an engine-driven work machine, an exhaust gas aftertreatment device is arranged vertically in a soundproof box, and an exhaust gas inlet provided on the upper end side of the exhaust gas aftertreatment device and an upper portion of the engine are provided. By connecting the exhaust port with an exhaust pipe, the distance from the exhaust port to the exhaust gas aftertreatment device is shortened, and the exhaust gas during introduction into the exhaust gas aftertreatment device is difficult to be cooled. Although an exhaust gas aftertreatment device is placed in an exhaust duct formed by partitioning the inside of a soundproof box or (Patent Document 3), the exhaust air is exhausted to a position where cooling air from the engine cooling fan is difficult to hit. There has also been proposed an engine-driven work machine in which an exhaust gas aftertreatment device is hardly cooled by disposing a gas aftertreatment device (Patent Document 4).

JP 2001-280118 A International Application PCT / JP2014 / 073178 Specification JP 2011-106287 A JP 2012-246771 A

  As described above, in the exhaust gas aftertreatment device, although PM is removed by continuous regeneration performed during normal operation, the exhaust gas aftertreatment device continues to operate at a low load where the exhaust gas aftertreatment device does not perform the function of continuous regeneration. For example, when PM deposition progresses on the DPF, the above-described forced regeneration (load variation type, constant load type) needs to be performed.

  In addition, if PM accumulation on the DPF further progresses and exhaust resistance of the entire exhaust gas flow path further increases despite the forced regeneration, the engine attached to the engine due to a decrease in engine output or an abnormal increase in exhaust temperature. In addition to causing malfunctions in the equipment (for example, burn-in of the supercharger), a large amount of accumulated PM starts self-combustion, so exhaust gas aftertreatment due to heat generated during combustion, and other components of the exhaust system Since the amount of PM deposited on the DPF further increases, the amount of PM deposited on the DPF increases to a predetermined deposition amount that is larger than the deposition amount that is the starting reference for the forced regeneration (load variation type, constant load type) described above. When it reaches, it is also necessary to take protective measures, such as displaying an alarm to warn the operator, or emergency stopping the engine.

  However, in either of the load fluctuation type or the constant load type forced regeneration described above, in order to perform the forced regeneration, it is necessary to forcibly raise the temperature of the DOC provided in the exhaust gas aftertreatment device to the activation temperature or higher. Yes, the forced regeneration methods described in the above-mentioned Patent Documents 1 and 2 adopt a configuration in which the exhaust gas temperature of the engine is increased by delayed fuel injection or post-injection, and thereby the DOC temperature is raised above the activation temperature. doing.

  Therefore, compared with normal operation, the engine during forced regeneration consumes extra fuel as much as post-injection, etc., resulting in poor fuel consumption and fuel consumption during forced regeneration, depending on the operating conditions. Increases by more than 10% compared to normal operation.

  In particular, in the constant load type forced regeneration, in order to realize the operation of the engine with a constant load, during the forced regeneration, the original work (for example, in the case of an engine driven generator, the power to the connected electrical equipment is A large amount of fuel is consumed only to regenerate the DPF.

  Further, when the PM accumulation amount on the DPF exceeds the accumulation amount that is the execution standard of the above-mentioned forced regeneration and the PM is burned, the exhaust gas aftertreatment device and other exhaust system configurations are generated by the heat generated during the combustion. When it reaches a level that may cause burnout to the equipment, it will not be possible to remove PM by combustion, so the engine-driven work machine is emergency stopped and the exhaust gas aftertreatment device is disassembled and cleaned, or The work using the engine-driven work machine is stopped during this period, and the cost of repairing parts such as replacement, cleaning, and maintenance work is forced, resulting in an increase in running cost. It becomes.

  Therefore, if PM accumulation on the DPF can be prevented, the fuel efficiency of the engine-driven work machine can be greatly improved by reducing the frequency of forced regeneration, and an emergency stop of the engine-driven work machine can be achieved. The cost and labor burden associated with disassembly cleaning and replacement of the exhaust gas aftertreatment device can be reduced.

  Here, in order to prevent PM accumulation from proceeding with respect to the DPF, it is only necessary to improve the PM removal efficiency in the continuous regeneration performed during the normal operation. In order to improve, it is only necessary to increase the inlet temperature of the DOC during normal operation so that the DOC can be maintained above the activation temperature for a longer time.

  Here, in Patent Document 3 described above, the temperature of the exhaust gas when passing through the exhaust pipe is prevented by shortening the length of the exhaust pipe communicating between the engine and the exhaust gas aftertreatment device.

  Moreover, in patent document 4, the temperature drop of the DOC in an exhaust-gas post-processing apparatus is prevented by heat-exchange with a cooling wind by making a cooling wind not directly hit an exhaust-gas post-processing apparatus.

  Therefore, in the configurations described in Patent Documents 3 and 4, by preventing the temperature from being lowered, the DOC temperature can be raised by the temperature that would otherwise have been lowered.

  However, in the configurations described in Patent Documents 3 and 4, only the passive means of preventing the above-described temperature decrease is employed, and since no configuration for positively raising the DOC temperature is provided, normal operation is not performed. Even if the amount of PM removed by continuous regeneration sometimes increases, a significant increase cannot be expected.

  Moreover, in Patent Documents 3 and 4, since the exhaust gas is transferred from the exhaust port of the engine to the exhaust gas aftertreatment device through the exhaust pipe, the exhaust gas still remains as cooling air when moving in the exhaust pipe. Because it is cooled by heat exchange, especially in cold areas, such as in cold areas, it becomes more prominently cooled. Therefore, the depolarization means of preventing the temperature drop of the exhaust gas introduced into the DOC is never enough. It cannot be said that it is a thing, and the effect obtained also in this respect is limited.

  The above-mentioned Patent Documents 3 and 4 do not describe the forced regeneration of the exhaust gas aftertreatment device. However, the above-mentioned forced drive engine equipped with the exhaust system described in Patent Documents 3 and 4 described above. When regeneration is performed, a new problem arises in that during exhaustive regeneration, a loud exhaust sound is generated and noise is worsened.

  That is, at the time of forced regeneration in which PM accumulated in the DPF is burned more than a predetermined amount, the exhaust gas temperature after passing through the DPF greatly increases due to the heat generated by the combustion of PM, and the volume of the exhaust gas increases with this temperature increase. Also expands.

  Therefore, as described in Patent Documents 3 and 4, in the configuration in which the exhaust gas that has passed through the exhaust gas aftertreatment device is discharged to the outside through the tail pipe, the flow rate of the exhaust gas at the outlet of the tail pipe However, it is difficult to sufficiently reduce the exhaust noise that has been increased in this way simply by installing a silencer, which is a cause of noise deterioration. It becomes.

  Therefore, the present invention has been made to solve the above-mentioned drawbacks of the prior art, and while having a relatively simple configuration, the PM removal efficiency in continuous regeneration performed during normal operation is improved, and forced regeneration is performed. By providing an exhaust system that can reduce the frequency of implementation and quiet the exhaust sound even during forced regeneration, it improves fuel consumption, lowers running costs, and reduces noise in engine-driven work machines It aims at realizing simultaneously.

  Hereinafter, means for solving the problem will be described together with reference numerals used in the embodiment for carrying out the invention. This symbol is used to clarify the correspondence between the description of the scope of claims and the description of the mode for carrying out the invention. Needless to say, it is used in a limited manner for the interpretation of the technical scope of the present invention. It is not a thing.

In order to achieve the above object, an exhaust system 30 for an engine-driven work machine according to the present invention includes:
One chamber in the soundproof box 10 divided into two chambers by the partition wall 13 forms an engine chamber 10a that houses the engine 20 and the work implement 3, and the other chamber has a communication port 14 provided in the partition wall 13. Is provided in the engine-driven work machine 1 as a discharge chamber 10b for guiding cooling air introduced from the engine chamber 10a to the outside of the machine, and is provided with an oxidation catalyst (DOC) on the inside of the inlet 31a and on the inside of the outlet 31b. In an exhaust system 30 equipped with a continuously regenerative exhaust gas aftertreatment device 31 containing a diesel particulate filter (DPF) that collects particulate matter (PM) contained in the exhaust gas of the engine. ,
The exhaust gas aftertreatment device 31 is disposed near the exhaust port 23 of the engine 20 in the engine chamber 10 a, and the inlet 31 a of the exhaust gas aftertreatment device 31 communicates with the exhaust port 23 of the engine 20. And
One end of an exhaust pipe 32 communicates with the outlet 31b of the exhaust gas aftertreatment device 31, and the other end of the exhaust pipe 32 extends through the partition wall 13 into the exhaust air chamber 10b.
The other end of the exhaust pipe communicates with an inlet of a silencer 33 accommodated in the exhaust chamber 10b.
One end of the tail pipe 34 communicates with the outlet of the silencer 33, and the other end of the tail pipe 34 is opened toward the outside of the soundproof box 10 (Claim 1).

  In the exhaust system 30 configured as described above, the exhaust gas aftertreatment device 31 is mounted on the engine 20, and the inlet 31 a of the exhaust gas aftertreatment device 31 is directly connected to the exhaust port 23 of the engine 20. It is preferable to adopt an attached configuration (claim 2).

  Furthermore, it is preferable to arrange the silencer 33 in the exhaust chamber 10b so that the longitudinal direction of the silencer 33 is orthogonal to the flow of cooling air passing through the exhaust chamber 10b ( Claim 3).

  With the configuration of the present invention described above, the engine-driven working machine 1 provided with the exhaust system 30 of the present invention can obtain the following remarkable effects.

  The exhaust gas aftertreatment device 31 accommodated in the engine chamber 10a is provided near the exhaust port 23 of the engine 20 so that the exhaust port 23 of the engine 20 and the inlet 31a of the exhaust gas aftertreatment device 31 communicate with each other. In addition to being able to introduce the gas into the exhaust gas aftertreatment device 31 without lowering the temperature, the exhaust resistance of the exhaust system 30 as a whole is increased by providing the silencer 33 in the configuration of the exhaust system 30. As a result, the temperature of the exhaust gas discharged from the exhaust port 23 of the engine 20 increased, and as a result, the DOC inlet temperature of the exhaust gas aftertreatment device 31 could be significantly increased compared to the conventional structure. .

  As a result, compared to the conventional structure, continuous regeneration is performed even in a lower load operating state, and the amount of PM removed by continuous regeneration during normal operation increases, so that PM accumulation was less likely to occur, and the frequency of forced regeneration could be reduced.

  As described above, since the frequency of forced regeneration that consumes a large amount of fuel can be reduced, the fuel consumption of the engine-driven work machine 1 can be greatly improved, and the running of the engine-driven work machine 1 can be improved. Cost could be reduced.

  Further, as described above, the DOC inlet temperature of the exhaust gas aftertreatment device 31 is increased, so that when the forced regeneration is performed, the DOC can be raised to the activation temperature in a short time. In addition, when performing control to increase or decrease the injection amount of the post-injection during forced regeneration according to the DOC inlet temperature, the DOC is raised to the activation temperature by a smaller amount of fuel injection (post-injection, etc.) This makes it possible to reduce fuel consumption during forced regeneration.

  In addition, when the exhaust gas aftertreatment device 31 is forcibly regenerated, although the exhaust gas that has passed through the DPF of the exhaust gas aftertreatment device becomes hot due to combustion of PM accumulated in the DPF and the volume expands, the exhaust gas aftertreatment device 31 is used as the engine. The chamber 10a and the silencer 33 are arranged apart from the exhaust chamber 10b, and the exhaust gas aftertreatment device 31 and the silencer 33 are communicated by the exhaust pipe 32, so that the outlet 31b of the exhaust gas aftertreatment device 31 is provided. The expanded exhaust gas that has exited the exhaust pipe 32 is introduced into the silencer 33 after its volume contracts due to heat exchange with the cooling air flowing in the soundproof box 10 when it passes through the exhaust pipe 32 and is cooled. The silencer 33 can be effectively silenced, and the volume is further shrunk by cooling when passing through the silencer 33 cooled by the cooling air in the exhaust chamber 10b. Since the exhaust gas is discharged through the tail pipe 34, the flow rate of the exhaust gas passing through the outlet of the tail pipe 34 is greatly reduced, and in combination with the silencing effect of the silencer 33, the forced regeneration is performed. The exhaust noise can be greatly reduced.

  When the exhaust gas aftertreatment device 31 is mounted on the engine 20 and the inlet 31a of the exhaust gas aftertreatment device 31 is directly attached to the exhaust port 23 of the engine 20, the engine 20 The exhaust gas from can be introduced into the DOC of the exhaust gas aftertreatment device 31 with the exhausted temperature as it is, and a decrease in the exhaust temperature can be prevented more reliably.

  In the configuration in which the silencer 33 is disposed in the exhaust chamber 10b so that the longitudinal direction of the silencer 33 is orthogonal to the flow of cooling air passing through the exhaust chamber 10b, the silencer 33 is cooled. As a result of efficient cooling by the wind, the volume of the exhaust gas in the silencer 33 is reduced favorably, and as a result, it is possible to further reduce the exhaust noise.

The plane perspective view of the engine drive type working machine provided with the exhaust system of the present invention. 1 is a front perspective view of an engine-driven work machine equipped with an exhaust system of the present invention. The graph which showed typically the relationship between the change of the load concerning an engine (change of generated electric power), and the change of DOC inlet temperature in this invention and the conventional exhaust system. The graph which showed typically the relationship of the change of the inlet temperature of DOC with respect to the change of the deposition amount of PM in this invention and the conventional exhaust system.

  Hereinafter, an engine-driven working machine 1 including an exhaust system 30 of the present invention will be described with reference to the accompanying drawings.

[Overall configuration of engine-driven work machine]
1 and 2, reference numeral 1 denotes an engine-driven work machine equipped with the exhaust system 30 of the present invention. The engine-driven work machine 1 is placed in a soundproof box 10 constituted by a frame 11 and a bonnet 12. A package-type engine-driven work machine 1 containing necessary equipment is configured.

  The above-described frame 11 constituting the soundproof box 10 is a base on which the components of the engine-driven work machine 1 are mounted. On this frame 11, an engine 20, a generator driven by the engine 20, In addition to the working machine 3 such as a compressor, the cooling fan 21, the radiator 22, and other components of the engine-driven working machine 1 are mounted, and the frame 11 on which these devices are mounted is covered with a box-shaped bonnet 12. It is packaged by that.

  The space in the soundproof box 10 is divided into two chambers, an engine chamber 10a and an exhaust chamber 10b, by a partition wall 13, and the engine 20 and the work implement 3 are accommodated in the engine chamber 10a. In the exhaust chamber 10b, a silencer 33 among the devices constituting the exhaust system 30 of the present invention is accommodated.

  The aforementioned partition wall 13 has a communication port 14 communicating with the engine chamber 10a and the exhaust chamber 10b, and a radiator 22 that heats the cooling water that has cooled the engine 20 facing the communication port 14. And a cooling fan 21 that generates cooling air toward the radiator 22 is disposed in the engine compartment 10a.

  Therefore, when the cooling fan 21 rotates and cooling air is generated, the air in the engine chamber 10a passes through the radiator 22 and is heat-exchanged with the cooling water in the radiator 22 and then introduced into the exhaust air chamber 10b. It is discharged out of the soundproof box 10 through an air vent 15 provided in the upper part of the exhaust chamber 10b.

  In the illustrated example, the air outlet 15 is provided in the upper portion of the exhaust chamber 10b. However, the arrangement of the air outlet 15 is not limited to this position, and the side wall of the bonnet 12 that forms the side wall of the exhaust chamber 10b. It is good also as what is provided in.

[Exhaust system]
The exhaust gas discharged from the exhaust port 23 of the engine 20 accommodated in the engine chamber 10a is discharged outside the machine through an exhaust system 30 extending from the engine chamber 10a to the exhaust chamber 10b.

  In the engine-driven work machine 1 of the present invention, the exhaust system 30 includes an exhaust gas aftertreatment device 31, a silencer 33 into which exhaust gas after passing through the exhaust gas aftertreatment device 31 is introduced, and the exhaust gas. The exhaust pipe 32 communicates between the post-processing device 31 and the silencer 33, and the tail pipe 34 that discharges the exhaust gas that has passed through the silencer 33 to the outside of the soundproof box 10.

  The exhaust gas aftertreatment device 31 described above is configured as the “continuous regeneration type” described as the prior art, and an oxidation catalyst (DOC) is provided on the inlet 31a side in the casing configured to allow the exhaust gas to pass therethrough. And a diesel particulate filter (DPF) for collecting PM contained in the exhaust gas is accommodated on the outlet 31b side with respect to the DOC.

  The exhaust gas aftertreatment device 31 is disposed in the engine chamber 10 a near the exhaust port 23 of the engine 20, and the inlet 31 a of the exhaust gas aftertreatment device 31 is communicated with the exhaust port 23 of the engine 20 at this position. The exhaust gas of the engine 20 can be introduced into the exhaust gas aftertreatment device 31 without causing a decrease in temperature.

  Preferably, the exhaust gas aftertreatment device 31 is mounted on the engine 20 in the immediate vicinity of the exhaust port 23 (on the flywheel housing of the engine in the illustrated example), and directly after the exhaust gas to the exhaust port 23 of the engine 20. The inlet 31a of the processing device 31 is connected.

  One end of an exhaust pipe 32 is connected to the outlet 31b of the exhaust gas aftertreatment device 31 in which the inlet 31a is connected to the exhaust port 23 of the engine 20, and the outlet 31b passes through the exhaust gas aftertreatment device 31. The exhaust gas discharged from the exhaust gas passes through the partition wall 13 and enters the silencer 33 accommodated in the exhaust air chamber 10b through the exhaust pipe 32 having the other end extended into the exhaust air chamber 10b. be introduced.

  As introduced in Patent Documents 3 and 4, the exhaust gas exhaust gas discharged from the exhaust port of the engine is introduced into an exhaust gas aftertreatment device provided at a position away from the exhaust port by an exhaust pipe. If it is desired to prevent the temperature of the exhaust gas introduced into the equipment from dropping during the transfer, for example, the exhaust pipe should have a double-pipe structure or be covered with a heat insulating material. In the exhaust system 30 of the embodiment, the exhaust gas aftertreatment device 31 is directly connected to the exhaust port 23 of the engine 20 without using an exhaust pipe or the like, while the exhaust pipe 32 is configured to communicate with the exhaust gas aftertreatment device. Since the exhaust gas after passing through 31 is adopted as a configuration for introducing the silencer 33 into the silencer 33, the temperature of the exhaust gas passing through the inside of the exhaust pipe 32 is rather lowered. Can Masui.

  Therefore, in the exhaust system 30 of the present invention, the exhaust pipe 32 does not need to have a double pipe structure or a heat insulation structure such as covered with a heat insulation material, and preferably passes through the exhaust pipe 32. In order to further reduce the exhaust gas temperature, the exhaust pipe 32 is disposed in a portion of the soundproof box 10 that serves as a cooling air flow path, or the exhaust pipe 32 is made of a material having good thermal conductivity. Further, a fin tube having a heat radiating fin attached to the outer periphery may be adopted as the exhaust pipe 32.

  The other end of the exhaust pipe 32 penetrating the partition wall 13 and extending into the exhaust chamber 10b communicates with the inlet of the silencer 33 accommodated in the exhaust chamber 10b.

  As the silencer 33, a multistage expansion silencer having a high silencing effect is employed in the present embodiment, but the structure of the silencer is not limited to this, and various known structures can be employed. It is.

  The muffler 33 has a substantially cylindrical shape in the illustrated form, and is preferably arranged so that its longitudinal direction is perpendicular to the flow of cooling air passing through the exhaust chamber 10b. In the illustrated embodiment in which the vent 15 is provided in the top plate of the exhaust chamber 10b and the cooling air is discharged upward, the silencer 33 is disposed in the horizontal direction near the vent 15 in the horizontal direction. By arranging so that it can be cooled, it can be cooled well by heat exchange with cooling air.

  A tail pipe 34 is communicated with the outlet of the silencer 33 described above, and the outlet of the tail pipe 34 is opened to the outside of the soundproof box 10 so that the exhaust gas after passing through the silencer 33 is passed through the soundproof box. 10 is configured to be able to exhaust outside.

  In the illustrated embodiment, the tail pipe 34 is configured to open toward the outside of the soundproof box 10 through the air outlet 15 formed in the upper portion of the exhaust chamber 10b. Is not limited to this configuration, and may be opened toward the outside of the soundproof box 10 through a through hole provided in the side wall of the soundproof box 10, for example.

  In the exhaust system of the conventional engine-driven working machine introduced as Patent Document 3 and Patent Document 4, exhaust gas discharged from the exhaust port of the engine is passed through an exhaust pipe, an exhaust gas aftertreatment device, and a tail pipe. In the exhaust system 30 of the present invention, the exhaust gas discharged from the exhaust port 23 of the engine 20 is exhausted from the exhaust gas aftertreatment device 31, the exhaust pipe 32, the silencer 33, and the tail. The exhaust gas is discharged through the pipe 34, and the exhaust resistance of the exhaust system 30 as a whole is increased by adding the silencer 33.

  In the exhaust system 30 of the present invention, the increase in the exhaust gas temperature of the engine 20 due to the increase in exhaust resistance is used to increase the DOC inlet temperature of the exhaust gas aftertreatment device 31 to improve the regeneration efficiency of the DPF. However, an excessive increase in the exhaust resistance is caused by a decrease in the output of the engine 20 or an excessive increase in the exhaust gas temperature, which heats the devices constituting the exhaust system 30 or the devices provided in the vicinity of the exhaust system 30. In particular, in the case of an engine with a supercharger (exhaust turbine), an excessive rise in the exhaust gas temperature causes the supercharger to seize.

  For this reason, the engine 20 is set with an allowable upper limit value Rlim of exhaust resistance, and the exhaust resistance of the exhaust system 30 does not exceed the maximum value Rmax set lower than the allowable upper limit value Rlim by a predetermined margin. Set as follows.

  That is, the sum of the basic resistance Rb, which is the exhaust resistance of the exhaust system 30 in a state where no PM is deposited, and the increment Rp of the exhaust resistance when PM is allowed to accumulate in the DPF is less than the maximum value Rmax described above. (Rb + Rp ≦ Rmax) is set.

  Therefore, assuming that the maximum value Rmax of the exhaust resistance is set to the same value as that of the conventional exhaust system, in the exhaust system of the present invention, the basic resistance Rb is increased by the installation of the silencer 33. In comparison with this, the allowable exhaust resistance increment Rp, that is, the allowable amount of PM deposition is reduced.

[Action etc.]
(1) Operation during normal operation When the engine 20 of the engine-driven work machine 1 equipped with the exhaust system 30 of the present invention described above is operated, the exhaust gas generated with the combustion of fuel in the engine 20 is converted into the engine. 20 is discharged from the soundproof box 10 through the exhaust gas aftertreatment device 31, the exhaust pipe 32, the silencer 33, and the tail pipe 34.

  The temperature of the exhaust gas discharged from the engine 20 changes as the load on the engine 20 increases or decreases, and the load on the engine 20 is the amount of work performed by the work machine 3 (for example, if the work machine 3 is a generator, power is generated. As the power increases, it increases, but decreases as the workload decreases.

When the work machine 3 has a large amount of work and a high load is applied to the engine 20, the exhaust gas temperature discharged from the exhaust port 23 of the engine 20 is also high, and the exhaust gas temperature introduced into the exhaust gas aftertreatment device 31. However, the temperature is higher than the activation temperature of the DOC, and in the exhaust gas aftertreatment device 31, NO ₂ is generated by the catalytic action of the DOC, and the PM deposited on the DPF using this NO ₂ as an oxidizing agent burns. The above-described continuous playback function is exhibited.

  On the other hand, when the work machine 3 has a small amount of work and the engine 20 is operated at a low load, the exhaust gas temperature discharged from the exhaust port 23 of the engine 20 is also low.

  As described above, when the exhaust gas temperature of the engine 20 decreases and the DOC inlet temperature becomes lower than the temperature necessary for the activation of the DOC, the exhaust gas aftertreatment device 31 does not exhibit the function of continuous regeneration and is built in. Since the PM is only collected by the DPF that has been collected, the collected PM proceeds without being removed.

  When PM deposition progresses and the ventilation resistance of the DPF increases and the exhaust resistance of the exhaust system 30 as a whole increases, the temperature of the exhaust gas discharged from the exhaust port 23 of the engine 20 rises. When the temperature rise causes the inlet temperature of the DOC to rise to a temperature necessary for DOC activation, the exhaust gas aftertreatment device 31 performs the above-described continuous regeneration.

  Here, in order to completely remove the PM accumulated in the DPF by continuous regeneration, it is necessary to maintain the state above the activation temperature of the DOC until the PM accumulated in the DPF burns and the regeneration of the DPF is completed. However, in the structure of the conventional exhaust system, it is difficult to maintain the DOC at the activation temperature until the PM removal is completed in the low load operation. With the configuration of the exhaust system 30, the exhaust resistance of the exhaust system 30 as a whole has increased due to the installation of the silencer 33, and the exhaust gas from the engine 20 can be introduced into the aftertreatment device 31 without causing a temperature drop. As a result, the amount of PM that can be removed during continuous regeneration can be increased.

  This point will be described in more detail with reference to FIG. 3 and FIG. 4. The graph shown by the alternate long and short dash line in FIG. 3 shows a conventional exhaust system (no silencer, engine exhaust port and exhaust gas aftertreatment). FIG. 2 schematically shows the relationship between the generated power and the DOC inlet temperature in an engine-driven generator having a configuration in which the apparatus is separated, and the graph shown by a solid line includes the exhaust system 30 of the present invention. 3 schematically shows the relationship between the power generated by the engine-driven generator 1 and the DOC inlet temperature.

  Compared to the conventional exhaust system, the exhaust system 30 of the present invention has a configuration in which the exhaust gas aftertreatment device 31 is arranged near the exhaust port 23 of the engine 20 and an increase in exhaust resistance due to the addition of the silencer 33. As an example, a temperature increase of about 100 ° C. is obtained in the operating state when the maximum generated power gmax is generated.

  As a result, assuming that “X” on the vertical axis in FIG. 3 is the inlet temperature of the DOC necessary for DOC activation, in the conventional exhaust system, continuous regeneration is performed only when the generated power of the generator is g4 or more. Is executed.

  On the other hand, in the exhaust system 30 of the present invention, the DOC inlet temperature is shifted to the high temperature side, so that the DOC inlet temperature is already necessary for the activation of the DOC when the generated power of the generator is g1. As a result, the continuous regeneration area can be expanded to a range where the generated power is not less than g1 and less than g4, which was not performed in the conventional structure. As a result, the amount of PM removal during normal operation can be increased.

  Fig. 4 is a graph schematically showing the change in the amount of accumulated PM and the change in the DOC inlet temperature in an operating state with a constant engine load. In the figure, the one-dot chain line represents the conventional graph. The graph shown by the exhaust system and the solid line is for the exhaust system 30 of the present invention.

  As shown in FIG. 4, when the amount of PM deposited on the DPF increases and the ventilation resistance of the DPF increases, the exhaust resistance of the exhaust system 30 as a whole also increases. Therefore, the exhaust gas discharged from the exhaust port 23 of the engine 20 When the temperature rises, the DOC inlet temperature also rises, and when the DOC inlet temperature becomes equal to or higher than the temperature X ° C. necessary for DOC activation, PM combustion starts.

  Here, in the exhaust system of the conventional structure, if the PM accumulation amount does not exceed p4, the DOC inlet temperature does not exceed X ° C, and once the accumulation amount exceeds p4, PM combustion starts. However, if the accumulated amount falls below p4 due to PM being burned and removed, the air permeability of the DPF is restored, the exhaust resistance is lowered, and the inlet temperature of the DOC is lower than X ° C. Even if continuous regeneration is performed in this state, it is difficult to completely remove the PM deposited on the DPF (removal to less than p4).

  In contrast, in the exhaust system 30 of the present invention, the basic exhaust resistance of the exhaust system 30 is increased by the addition of the silencer 33, and the temperature of the DOC inlet is reduced by preventing the exhaust gas temperature from decreasing. Since it is shifted to the high temperature side, continuous regeneration is performed when PM accumulates over p1 on the DPF. Therefore, in the conventional structure, the amount of deposition is over p1 and less than p4 where continuous regeneration was not performed. The ability to expand the execution area of continuous regeneration makes it possible to increase the amount of PM removed during normal operation, and to remove PM until the amount of accumulated PM on the DPF becomes smaller. It is something that can be done.

  In addition, when the exhaust resistance of the entire exhaust system including the increase of the exhaust resistance accompanying the PM deposition of the DPF is the same, the PM deposition amount with respect to the DPF in the exhaust system 30 of the present invention is equal to the PM deposition amount in the conventional exhaust system. Since it is relatively small, PM can be completely removed in a shorter time, and in this respect, the deposited PM is easily removed.

  As described above, in the engine-driven work machine 1 provided with the exhaust system 30 of the present invention, the DPF regeneration is performed by continuous regeneration performed during normal operation, as compared with the engine-driven work machine provided with the conventional exhaust system. Can be completed, and both the load fluctuation type and the constant load type can be reduced, and the number of forced regenerations can be reduced. This reduces the fuel consumption associated with forced regeneration, thereby reducing the running cost. .

(2) Operation during forced regeneration As described above, in the engine-driven work machine 1 equipped with the exhaust system 30 of the present invention, PM can be efficiently removed by continuous regeneration performed during normal operation. , PM accumulation on the DPF is less likely to occur, and thus the frequency of forced regeneration can be reduced. However, even with an engine-driven work machine equipped with the exhaust system of the present invention, continuous regeneration is possible. When the operation at a low load which is not executed is performed for a long time, PM deposition can still proceed on the DPF.

  Therefore, the engine-driven work machine 1 equipped with the exhaust system 30 of the present invention needs to perform the above-described forced regeneration (load fluctuation type forced regeneration, constant load type forced regeneration).

  As an example, in the present embodiment, when the amount of PM deposited on the DPF exceeds a predetermined first accumulation amount, load fluctuation type forced regeneration is executed. If the PM deposition further progresses and exceeds the first deposition amount and exceeds the second deposition amount, the constant load type forced regeneration is performed, and further, the PM deposition amount exceeds the second deposition amount. When the amount exceeds 3 deposits, an alarm is displayed to warn the operator, or the engine is stopped, and the engine-driven work machine is protected.

  The engine-driven work machine equipped with the exhaust system of the present invention exhibits the following advantageous effects even during such forced regeneration.

(2-1) Improved fuel consumption during forced regeneration As described above, the engine-driven work machine 1 equipped with the exhaust system 30 of the present invention has a higher exhaust gas temperature than that of the conventional structure, and the DOC inlet temperature. As a result, the fuel consumption during forced regeneration can be reduced.

  That is, in the engine-driven working machine 1 equipped with the exhaust system 30 of the present invention, the exhaust gas temperature is high and the DOC inlet temperature has already increased, as described above. It is possible to increase the temperature to the temperature necessary for activating the DOC in a short time after the start of the operation, the execution time of forced regeneration is shortened, and the fuel consumption by post injection can be reduced. In addition, when the control is performed to detect the DOC inlet temperature and increase or decrease the fuel injection amount in the post-injection depending on the level of the inlet temperature, the fuel injection amount in the post-injection is reduced because the DOC inlet temperature is high. It is possible to reduce the fuel consumption due to the above.

  As a result, it becomes possible to perform forced regeneration by using a smaller amount of post-injection, etc., compared to an engine-driven work machine equipped with a conventional exhaust system. It was also possible to improve fuel efficiency during regeneration.

(2-2) Reduction of exhaust noise during forced regeneration Exhaust gas discharged from the outlet 31b of the exhaust gas aftertreatment device 31 compared to during normal operation due to combustion of PM accumulated in the DPF during forced regeneration. The temperature of the gas becomes high.

  An engine-driven work machine equipped with a conventional exhaust system has a structure in which exhaust gas that has undergone volume expansion due to high temperature after passing through an exhaust gas aftertreatment device is discharged outside the soundproof box through a tail pipe. Because it is adopted, the flow rate of the exhaust gas that passes through the outlet of the tail pipe becomes faster as the volume expands, and the exhaust noise becomes louder than during normal operation.

  On the other hand, in the engine-driven working machine 1 provided with the exhaust system 30 of the present invention, the exhaust gas that has passed through the exhaust gas aftertreatment device 31 passes through the partition wall 13 from the engine chamber 10a and the exhaust chamber. By adopting a structure that is introduced into the silencer 33 disposed in the exhaust chamber 10b through the exhaust pipe 32 extending to 10b, the exhaust sound can be suitably silenced.

  Here, the engine chamber 10a wall surface of the soundproof box 10 is provided with an intake port (not shown) for taking outside air into the engine chamber 10a. In addition to the intake air of the machine 3, the cooling fan 21 rotates to reach the exhaust chamber 10b from the engine chamber 10a through the communication port 14 and the radiator 22 provided in the partition wall 13 and then to the exhaust chamber 10b. The cooling air is discharged from the air outlet 15 to the outside of the soundproof box 10.

  Therefore, the cooling air described above is exhausted through the interior by heat exchange by contact with the exhaust pipe 32 communicated with the exhaust gas aftertreatment device 31 and the silencer 33 disposed in the exhaust air chamber 10b. Cool the gas.

  As a result, the exhaust gas that has been heated to a high temperature by the heat generated by the combustion of the PM deposited on the DPF and has expanded in volume and has exited the outlet 31b of the exhaust gas aftertreatment device 31 is cooled when passing through the exhaust pipe 32. Since the volume is shrunk and then introduced into the silencer 33, the silencing efficiency of the silencer 33 is improved, and the volume of the silencer 33 is cooled and further shrunk when passing through the silencer 33. The exhaust gas flow velocity passing through the outlet of the tail pipe 34 communicating with the exhaust pipe can be greatly reduced, and in combination with the silencing effect by the silencer 33, the exhaust noise can be greatly reduced even during forced regeneration. did it.

DESCRIPTION OF SYMBOLS 1 Engine drive type working machine 3 Working machine 10 Soundproof box 10a Engine room 10b Exhaust room 11 Frame 12 Bonnet 13 Partition wall 14 Communication port 15 Exhaust port 20 Engine 21 Cooling fan 22 Radiator 23 Exhaust port 30 Exhaust system 31 Exhaust gas Processing device 31a Inlet 31b Outlet 32 Exhaust pipe 33 Silencer 34 Tail pipe

Claims (3)

One chamber in the soundproof box divided into two chambers by the partition wall is formed as an engine chamber that houses the engine and the work machine, and the other chamber is connected to the engine chamber via a communication port provided in the partition wall. It is installed in an engine-driven work machine that serves as an exhaust chamber for guiding the introduced cooling air to the outside of the machine. It captures the oxidation catalyst inside the inlet side and the particulate matter contained in the engine exhaust gas inside the outlet side. In an exhaust system equipped with a continuously regenerative exhaust gas aftertreatment device that contains a diesel particulate filter
The exhaust gas aftertreatment device is disposed near the exhaust port of the engine in the engine chamber, and the inlet of the exhaust gas aftertreatment device is communicated with the exhaust port of the engine;
One end of an exhaust pipe communicates with the outlet of the exhaust gas aftertreatment device, and the other end of the exhaust pipe extends through the partition wall to the exhaust chamber,
The other end of the exhaust pipe communicates with an inlet of a silencer housed in the exhaust chamber,
An exhaust system for an engine-driven working machine, wherein one end of a tail pipe communicates with an outlet of the silencer, and the other end of the tail pipe is opened toward the outside of the soundproof box.   2. The engine-driven work machine according to claim 1, wherein the exhaust gas aftertreatment device is mounted on the engine, and the inlet of the exhaust gas aftertreatment device is directly attached to the exhaust port of the engine. Exhaust system.   The silencer is disposed in the exhaust chamber so that the longitudinal direction of the silencer is orthogonal to the flow of cooling air passing through the exhaust chamber. Exhaust system for engine-driven work machines.

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